Fodera, Sadowsky, aguilar, and other bass preamps

Stompboxes circuits published in magazines, books or on DIY electronics websites.

Re: Fodera, Sadowsky, aguilar, and other preamps

Postby lietuvis » 29 Oct 2012, 23:21

bajaman wrote:
where did you find them


All of them from ebay.
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Re: Fodera, Sadowsky, aguilar, and other preamps

Postby bajaman » 30 Oct 2012, 00:12

silly me - never thought to look there :slap:
I will draw the schematic and finalise the board layout tonight (and maybe the next few nights :wink: )
Will post it for everyone once completed. :D
cheers
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Re: Fodera, Sadowsky, aguilar, and other preamps

Postby darmstat » 02 Nov 2012, 15:49

Does anyone have a schematic of the Fodera Model 2000 Preamp ?
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Re: Fodera, Sadowsky, aguilar, and other preamps

Postby darmstat » 06 Nov 2012, 15:52

I hope this help with the Fender Trace.
Controls are master volume, pan, and three-band active EQ with treble boost/cut (+/- 10 db at 8kHz, a shift in the cut frequency, and about a 2dB slope per octave), mid boost/cut (+10dB, -15dB at 500Hz, and a wide band slope) and bass boost/cut (+/- 12db at 40Hz, with a 4dB slope per octave).

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Re: Fodera, Sadowsky, aguilar, and other preamps

Postby bajaman » 06 Nov 2012, 20:09

thanks darmstat :hug:
It would be nice to know the smd capacitor and resistor values :wink:
It does appear to be very similar to the MIJ Precision Lite preamp in many respects.
i have an smd board layout (single sided :D ) ready to publish, but just awaiting the missing values.
i simulated my guess last night - the treble boost frequency is VERY helpful - I already knew the mid and bass turnovers and they are exactly what you have provided in your post.
The input stage gain eludes me at present :( , but it does not seem to be that important - some of the pictures posted earlier from Ebay actually show this stage as a unity gain buffer :scratch:
More very soon
thanks for any help to come :thumbsup
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Re: Fodera, Sadowsky, aguilar, and other preamps

Postby lietuvis » 06 Nov 2012, 21:19

I think that SMD pcb is more universal: it can be unit gain or as a gain stage, eq section can be peaking or shelving. Depend on how to populate the PCB. That shows pictures from ebay. Something similar can be found on circuits for Carvin onboard bass preamps, some bass and treble there are set as shelving and some as peaking. And in fact I do not really use bass and treble (well sometimes I do roll off treble) but do really like to play with midrange control and I use ampeg cloned inductor with 5 position switch which gives me plenty of different colour sound to my bass. Would really like to get ampeg PF500 preamp schematic to clone it and simplify to build it as onboard preamp.
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Re: Fodera, Sadowsky, aguilar, and other preamps

Postby darmstat » 06 Nov 2012, 23:25

Well Bajaman....I have 3.75k,3.75k, and 4.75k for the mids and 11k, 11k, and 22k for bass so far.( Don't know if that is correct) It is very hard for me to see the treble values.
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Re: Fodera, Sadowsky, aguilar, and other preamps

Postby bajaman » 07 Nov 2012, 05:26

Hello darmstat :D
Thanks for that - i have played around with some values in my simulator - the capacitor across the treble control is most likely 470p to 560p or some weird smd value in between these :wink:
If I may be so bold, where did you get the turnover frequency information from and how accurate is it ?
(PM or email me if you want to keep your source confidential :wink: ).
Although lietuvis' pictures are very helpful, it is almost impossible to read the smd resistor values, but many of them appear to be the same as the MIJ lite schematic published a few pages back in this thread.
If your turnover frequencies are correct, then it will not be too hard for me to work out the correct component values, then I will publish the schematic AND single sided SMD board layout for all our members enjoyment.
Why do people insist on double sided board layouts for such a simple baxandall active tone control :scratch: :roll:
My single sided layout uses only three 0 ohm link smd resistors - I removed the other 0 ohm resistors showing on the Fender board :wink:
I also removed the diode in series with the +9v supply - if someone is stupid enough to connect the battery snap the wrong way round then it is their problem :lol:
cheers
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Re: Fodera, Sadowsky, aguilar, and other preamps

Postby darmstat » 07 Nov 2012, 05:42

Dave's repair shop. They gave me the information. I must note however that he told me that some of the fender 3 band use 12khz, but most common is the 8khz. This forum has helped me so i try to give back when i can. You seem to really know what you are doing, keep up the great work and thank you.... :D

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Re: Fodera, Sadowsky, aguilar, and other preamps

Postby darmstat » 07 Nov 2012, 05:47

You are correct. Single sided board is fine for the Baxandall 3 band eq.
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Re: Fodera, Sadowsky, aguilar, and other preamps

Postby bajaman » 07 Nov 2012, 06:00

This forum has helped me so i try to give back when i can.

:hug:
nicely put my friend :thumbsup
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Re: Fodera, Sadowsky, aguilar, and other preamps

Postby bajaman » 07 Nov 2012, 12:49

Fender American Standard Jazz Bass
Here is my best guess simulation schematic based on one of the images (the one showing a gain stage before the active tone control).
It's getting late at night (early morning here in NZ) so this is all I am going to post at present - more tomorrow :wink:
cheers
bajaman
multisim baja three band bass preamp 051112.png
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Re: Fodera, Sadowsky, aguilar, and other preamps

Postby darmstat » 07 Nov 2012, 15:45

All i can say Bajaman is " You Rock" I will breadboard it up tonight when i get home. Thanks :applause:

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Re: Fodera, Sadowsky, aguilar, and other preamps

Postby lietuvis » 07 Nov 2012, 17:53

bajaman wrote:Fender American Standard Jazz Bass
Here is my best guess simulation schematic based on one of the images (the one showing a gain stage before the active tone control).
It's getting late at night (early morning here in NZ) so this is all I am going to post at present - more tomorrow :wink:
cheers
bajaman

Hi Baja you added R25 to circuit as 2M2 but I think there is C12-220P instead and also C4-1n looks too large to me, will it cut most of high frequencies in gain stage?( I might be wrong)
Thanks for all your effort to trace the circuit :thumbsup
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Re: Fodera, Sadowsky, aguilar, and other preamps

Postby bajaman » 07 Nov 2012, 21:27

Hello lietuvis
R25 is correct for the particular circuit layout I traced - the one that shows it fitted in a Fender Jazz bass :wink:
There are several different versions of this circuit board - some have a unity buffer stage first, BUT the one I traced has the gain stage with the relatively large hf rolloff capacitor C4 fitted.
Without this 1n capacitor the hiss would be very annoying at full treble boost :wink: The Fender American Deluxe bass PDF circuit board image shows R25 and C12 even though only one of these components is fitted. On the board which I traced only C12 is marked on the silkscreen, BUT if you look at what is fitted it is clearly NOT a capacitor but a 2.2M resistor.
The inclusion of C9 (470n or 0.47u electro) on the circuit means there is now no direct DC path from the second stage op amp output to the inverting input - this is WHY C12 is replaced by R25, a 2.2M ohm resistor :secret: :wink:
With the gain stage resistor and capacitor values AND with all the tone controls set to mid way, the frequency response is -3dB down at approx 23Hz and 30KHz - it has a stage gain of 6.6dB (or x4.62 AC voltage gain) :wink: .

The pictures of the Fender preamp which you can purchase for US$60 on ebay is NOT this circuit - it has a buffer and several different value resistors fitted in the tone control section - it does NOT have the 470n capacitor fitted to the wiper of the bass control pot AND it has the C12 220p capacitor fitted instead of the 2.2M resistor :secret: :wink:

Back to the Fender American Deluxe bass circuit :wink:
I will publish some response curves showing full boost and full cut for each of the three bands of the tone controls soon.
Of course there is a good deal of interaction between these controls, which is normal for such a simple baxandall circuit.
To achieve proper separation involves three separate op amp stages :wink: :!:
For example: if you have full treble boost and then turn up the midrange it will actually cut the treble boost response down :shock:

All for now - have work to do :)
cheers
Steve

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Re: Fodera, Sadowsky, aguilar, and other preamps

Postby darmstat » 08 Nov 2012, 01:41

Hi Bajaman...I will try the schematic tonight, I did find a Benavente 3 band eq, I made a copy using Diy Layout Creator. It seems very like the MIJ Fender preamp with some adjusting of the values.
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Re: Fodera, Sadowsky, aguilar, and other preamps

Postby bajaman » 08 Nov 2012, 01:50

okay - here are some graphs :wink:
the first is normalized to all controls flat (mid way)
then: full bass boost, full bass cut, full mid boost, full mid cut, full treble boost, and finally full treble cut.
enjoy :D
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Re: Fodera, Sadowsky, aguilar, and other preamps

Postby darmstat » 08 Nov 2012, 01:55

I am about to breadboard it up...so it worked ok for you Bajaman?
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Re: Fodera, Sadowsky, aguilar, and other preamps

Postby Duckman » 08 Nov 2012, 04:22

Great job from Baja & Co :applause:
One question: can you point the pinout for the pots in your schematic?

Big thanks!
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Re: Fodera, Sadowsky, aguilar, and other preamps

Postby bajaman » 08 Nov 2012, 08:37

I am about to breadboard it up...so it worked ok for you Bajaman?

Only a simulation at present , but i do not see why it would not work properly in the physical realm :wink:

One question: can you point the pinout for the pots in your schematic?

sure :)
reading left to right on the schematic: pin 3, pin 2, pin 1 (where pin 3 is the clockwise pin, pin 2 is the wiper and pin 1 is the counter clockwise pin)
All the same :wink: ALL tone pots are 100k linear :wink:

Anyone up for the single sided SMD board layout then :?: :wink:
cheers
bajaman

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